There are three types of neutrinos: Electron, Muon and Tau Neutrinos.When I search for an explanation about what they are I get the answer that a Electron Neutrino is a Neutrino associated with an Electron and a Muon Neutrino is a Neutrino associated with a Muon. The same applies to a Tau Neutrino.

I would like to know what the word ''associated'' means in this case Thank you very much for reading!

Neutrinos were first detected in radioactive Beta capture (which absorbs an electron) and Beta decay (which produces a positron = anti-electron) - but there was some missing energy and momentum in the reaction. Fermi suggested that the missing energy was carried away by an unseen particle.

There were similar anomalies in later reactions involving Muons, and similarly when the Tau particle was discovered. This gave the three known neutrino types their names.

We now know that these associations are not "fixed", and that a given neutrino will oscillate between all three types as it travels through space at slightly less than the speed of light in a vacuum.